Separate type magnetic shield apparatus

ABSTRACT

It is an object of the present invention to provide a separate type magnetic shield apparatus which has high access performance to a magnetically shielded space, in which magnetic shielding is very effectively achieved. In the separate type magnetic shield apparatus, first and second conductors  10   a  and  10   b  extending in the longitudinal axial line direction are provided on a curved magnetic shield outer side wall  3  of a first magnetic shield side wall body  2 A at up and down symmetrical positions relative to the longitudinal plane Hp passing through the longitudinal axial line of the cylindrical space S to cause current to flow therethrough; first and second conductors  10   c  and  10   d  extending in the longitudinal axial line direction, on the curved magnetic shield outer side wall  3  of the second magnetic shield side wall body  2 B, at up and down symmetrical positions relative to the horizontal plane Hp passing through the longitudinal axial line of the cylindrical space S to cause current to flow therethrough; and magnetic fluxes H coming horizontally to the first magnetic shield side wall body  2 A and to the second magnetic shield side wall body  2 B are deflected up and down by means of magnetic fields produced around the first and second conductors  10   a,    10   b,    10   c  and  10   d,  thereby preventing magnetic fluxes from flowing into the cylindrical space S.

TECHNICAL FIELD

The present invention relates to a separate type magnetic shieldapparatus applicable, for example, as an electronic beam exposureapparatus, measures taken for environmental magnetic field of anelectron microscope, and in the area of measurement, human cerebralmagnetic field, cardiac magnetic field measurement, furthermore, animalbiological magnetism measurement, and moreover, measurement in thenano-bio-area in which magnetic beads are used as labels.

BACKGROUND ART

For example, the magnetic field emitted from a human body such as thatfrom brain or heart contains many important real-time biological piecesof information. When the cardiac magnetic field detected by a MCGdetector such as 64 channel SQUID gradiometers, the electrophysiologicalfunction of heart can be two-dimensionally mapped. It is furthermorepossible to obtain overwhelmingly more accurate and more diversediagnostic pieces of information than those available by the methodbased on waveform analysis of electrocardiograph, such as time and spaceinformation of current vector flowing along the irritation conductionsystem.

Acute myocardiac infarction which is an epitome of ischemic heartdiseases is believed to be one of the three major causes of death ofJapanese. Expensive high-tech medical technologies are used for the curethereof. If more accurate and more rapid diagnosis is possible, it wouldbring about considerable effects not only in the remarkable reduction ofmedical cost but also in life-saving.

Partly because of the lapse of only a short period of time fromdevelopment of the magnetocardiograph, its popularization is still in aninitial stage in spite of these rich potentialities.

One of the causes of this slow progress of popularization lies in achamber type magnetic shield room made of permalloy which is expensiveand inconvenient. The magnetic screening performance is not required tobe so high as that required for cerebral magnetic field measurement, buthere is an increasing demand for a flexible magnetic shield apparatuswhich permits measurement by bringing the patient together with his orher bed.

In other words, there is a demand for development of a separate movabletype high-performance magnetic shield apparatus, not of the chambertype, which is applicable without difficulty for the measurement ofbiological magnetism such as cardiac magnetic field issued not only froma healthy person, but also from a bedridden patient.

The present inventors have therefore developed many componenttechnologies for the purpose of developing a cylindrical-type light andhigh-performance magnetic shield apparatus. A magnetic shakingtechnology (Non-Patent Document 1); leakage inhibition of shakingmagnetic field (Non-Patent Document 2); inhibition of magnetic noisecaused by an external cause entering from an opening end (Non-PatentDocuments 3 and 4); and further, integral forming of magnetic shieldbased on lamination structure using a carbon fiber reinforced plastics(CFRP) (Patent Document 1) are included.

In general, installation of a chamber-type shield apparatus afterward inthe room results in a difference in floor height so that it is not easyto carry the patient, together with his or her bed, into the apparatus.

It is therefore suggested to simply divide the cylindrical shield intotwo and to make it movable as described in Patent Document 2. FIG. 12illustrates an example of the separate type shield apparatus 100 havinga structure in which divided pieces are arranged one to the right andthe other to the left, and are joined at upper and lower positions.

According to this example, the separate type shield apparatus 100 has astructure in which at least any of two magnetic shield divided bodies101 (101A and 101B) formed in a right-left-symmetrical shape is mademovable to permit transportation of a patient together with his or herbed into the inner space.

However, the function of magnetic shield cannot be maintained with thisconfiguration alone. Since, in the separate type shield apparatus 100,it is necessary to install SQUID gradiometers 200, and a space is formedat the joint between the two divided bodies 101A and 101B. Therefore,magnetic fluxes passing through this space (i.e., magnetic fluxesperpendicular to the joint) cannot be passed continuously, and themagnetic shielding effect fails here.

-   Patent Document 1: Japanese Patent Application No. 2005-80775-   Patent Document 2: Japanese Patent Application Laid-Open No.    2004-179550-   Non-Patent Document 1: Ichiro SASADA, study on magnetic shaking type    magnetic shield for measuring weak magnetic fields, Journal of Japan    Applied Magnetism Society, 27,855-861 (2003)-   Non-Patent Document 2: Nakashima Y, Kimura T, Sasada I, Magnetic    field leakage from a 45° angle magnetic shell and a reduction method    for a high-performance magnetic shield, IEEE Trans. on Magn.    42(10)3545-3547 (2006)-   Non-Patent Document 3: Saito T, Tashiro N, Sasada I, Active    compensation effect in multi-shell shield with passive shell,    Journal of Japan Applied Magnetism, 29, 567-570 (2005)-   Non-Patent Document 4: Umeda Y, Tashiro N, Sasada I, Application of    active cancellation to cylindrical magnetic shield, Electricity    Society A, 123, (8), 790-796 (2003)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

It is an object of the present invention to solve the above-mentionedproblems posed by the separate type shield apparatus having theconfiguration as shown in FIG. 12. At the same time, it is also anotherobject of the present invention to provide a simple, compact andhigh-performance magnetic shield having a configuration in whichdisturbing magnetic fields are deflected not to enter into the space tobe shielded by actively produced magnetic fluxes, and magnetic bodiesare partially arranged to prevent the actively produced magnetic fieldsfrom entering the space to be shielded.

In general, a method popularly used at the time of creating a spacehaving a low magnetic flux density in a case where magnetic fluxes areuniformly present is to flow current into conductors in the direction inwhich magnetic fluxes are to be ejected by arranging conductors in thespace. A case where optimization is achieved by this method isillustrated in FIG. 11( a).

In this example, four conductors 10 (10 a, 10 b, 10 c and 10 d) arearranged at prescribed intervals at up-down and right-left symmetricalpositions. In the drawing, current flows through the conductors 10 a and10 c from the near side to the far side, and flows through theconductors 10 b and 10 d from the far side to the near side. For thehorizontal magnetic flux H entering from left to right in FIG. 11( a),the magnetic flux line density is lower at the center portion S of thespace surrounded by the four conductors 10 (10 a, 10 b, 10 c and 10 d),and it is known that magnetic shielding is accomplished there.

FIG. 11( b) illustrates, on the other hand, a configuration in whichfour magnetic plates A, B, C and D are arranged in a rectangular shapeby providing a gap G at positions neighboring each other. In thisconfiguration, most magnetic fluxes pass through the center portion, andthe shielding effect is unavailable.

However, the configuration shown in FIG. 11( c) is achieved by combiningthe configuration of FIG. 11( a) and that of FIG. 11( b). As shown inFIG. 11( c), a portion where the magnetic flux line density is low atthe center portion S of the space surrounded by four magnetic bodyplates A, B, C and D is formed in this configuration, and it is revealedthat a high shielding ratio unexpected at all is available here.

The cause is that the magnetic fluxes are expelled by means of thecurrent flowing through the conductors 10 a, 10 b, lac and 10 d, andsimultaneously, unnecessary magnetic fluxes are prevented from lappingout by the magnetic bodies A, B, C and D on the side of the space to beshielded (center portion S).

The possibility was thus revealed to localize the effect of excludingmagnetic fluxes by the current to a particular direction, by properlydesigning the relationship between current and the magnetic bodies.

More specifically, in the configuration shown in FIG. 11( c), a combinedstructure of the two conductors 10 a and 10 c provided at upperpositions and the magnetic body plates A and C expel the magnetic fluxline H upward, and a combined structure of the two conductors 10 b and10 d and the magnetic body plates B and D expel the magnetic flux line Hdownward, thus causing generation of a wide magnetic shield space S atthe center.

The present invention is based on a novel finding of the presentinventors as described above that proper combination of the currentaction and the action of magnetic bodies makes it possible to veryeffectively achieve a magnetic shield.

An object of the present invention is to provide a separate typemagnetic shield apparatus which has a high access property to a magneticshielding space and permit effective achievement of magnetic shielding.

Means for Solving the Problems

The above-mentioned objects of the present invention are achievable byuse of the separate type magnetic shield apparatus of the presentinvention. In short, according to the present invention, there isprovided a separate-type magnetic shield apparatus, having a pluralityof magnetic shield side wall bodies in the longitudinal direction;wherein the plurality of magnetic shield side wall bodies are combinedmutually to form therein a substantially cylindrical space around thelongitudinal axial line extending horizontally, and at least one of themagnetic shield side wall bodies moving relative to the remainingmagnetic shield side wall bodies is made separable;

wherein each of the plurality of magnetic shield side wall bodies has amagnetic shield outer side wall body having one of the magnetic bodieswhich are combined mutually to form therein the cylindrical space, andjoint magnetic shield side walls having magnetic bodies which projectfrom the both longitudinal end edges of the magnetic shield outer walloutwardly in the radial direction to the cylindrical space;

and wherein conductors extending in the longitudinal axial direction ofthe cylindrical space are provided on the magnetic shield outer wall ofthe magnetic shield side wall body to supply current therethrough;

and whereby disturbing magnetic fluxes coming from the magnetic shieldside wall body on one side horizontally to the magnetic shield side wallbody on the other side are deflected upwardly or downwardly by means ofthe magnetic field produced around the conductors to thereby prevent themagnetic fluxes from flowing into the cylindrical space.

According to an embodiment of the present invention, a plurality ofbulkhead magnetic shield members having magnetic bodies are arrangedbetween facing joint magnetic side walls of neighboring magnetic shieldside wall bodies.

According to another embodiment of the present invention, the magneticshield outer side wall and the joint magnetic shield side wall areformed by providing magnetic bodies on a support.

According to another embodiment of the present invention, the bulkheadmagnetic shield members are formed by providing magnetic bodies on asupport.

According to another embodiment of the present invention, a coil iswound in the longitudinal direction thereof and in a toroidal shapearound the magnetic shield side wall body, and magnetic shaking currentis supplied thereto.

According to another embodiment of the present invention, a magneticshield flange is provided at each of the both-end openings in thelongitudinal direction of each magnetic shield side wall body, therebypreventing magnetic fluxes from flowing into the cylindrical space fromthe longitudinal end openings of the magnetic shield side wall body.

According to another embodiment of the present invention, the magneticshield flange member is formed by providing a magnetic body on asupport.

According to another embodiment of the present invention, a coil isinstalled on the magnetic shield flange member to cause current to flowtherethrough, thereby preventing magnetic fluxes from flowing into thecylindrical space from the longitudinal openings of the magnetic shieldside wall body.

According to another embodiment of the present invention, a coil iswound around the joint magnetic shield side wall oppositely arranged ofthe neighboring magnetic shield bodies in the axial direction, andcurrent is supplied therethrough, thereby preventing magnetic fluxesfrom flowing from the gap formed between the joint magnetic shield sidewalls arranged oppositely of the neighboring magnetic shield side wallbodies.

According to another embodiment of the present invention, thecylindrical space is formed by being surrounded by two, four, six oreight magnetic shield wall bodies.

According to another embodiment of the present invention, the magneticshield side wall bodies surrounding the cylindrical space have anidentical size and shape.

According to a preferred embodiment of the present invention, there isprovided a separate type magnetic shield apparatus comprising a firstmagnetic shield side wall body and a second magnetic shield side wallbody; wherein the first magnetic shield side wall body and the secondmagnetic shield side wall body form a substantially cylindrical spacearound the longitudinal axial line extending horizontally in theinterior in an oppositely arranged state; and at least any of themagnetic shield side wall bodies moves and is separable from the othermagnetic shield side wall body;

wherein the first and second magnetic shield side wall bodies each has acurved magnetic shield outer side wall which has a magnetic body formingthe cylindrical space in the interior in the oppositely arranged state,and joint magnetic shield side walls having magnetic bodies whichproject vertically from the upper and lower end edges of the curvedmagnetic shield outer side wall and are spaced apart from each other andfacing each other in a oppositely arranged state;

wherein first and second conductors extending in the longitudinal axialline direction are provided on the curved magnetic shield outer sidewall of the-first magnetic shield side wall body to cause current toflow;

wherein first and second conductors extending in the longitudinal axialline are provided on the curved magnetic shield outer side wall of thesecond magnetic shield side wall body to cause current to flow;

and whereby disturbing magnetic fluxes coming from the first magneticshield side wall body horizontally to the second magnetic shield sidewall body are deflected up and down by means of magnetic fluxes producedaround the first and second conductors, thereby preventing the magneticfluxes from flowing into the cylindrical space.

Preferably, according to an embodiment, the first magnetic shield sidewall body and the second magnetic shield side wall body have right-leftsymmetric shapes relative to a vertical plane passing through thelongitudinal axial line of the cylindrical space.

According to another embodiment, a plurality of bulkhead magnetic shieldmembers each having a magnetic body arranged between the joint magneticshield side walls opposing to each other of the first and secondmagnetic shield side wall bodies.

According to another embodiment, the curved magnetic shield outer sidewall and the joint magnetic shield side wall are formed by providing amagnetic body in each of the supports.

According to another embodiment, the bulkhead magnetic shield member isformed by providing a magnetic body in each support.

According to another embodiment, a coil is wound in a toroidal shape inthe axial line direction around the first and second shield side wallbodies.

According to another embodiment, magnetic shield flange members areprovided in the axial direction end openings of the first and secondshield side wall bodies, thereby preventing magnetic fluxes from flowingfrom the axial-direction end openings of the first and second shieldside wall bodies into the cylindrical space.

According to another embodiment, the magnetic shield flange member isformed by providing a magnetic body in each of the supports.

According to another embodiment, a coil is installed on the magneticshield flange member to cause current to flow therethrough, therebypreventing magnetic fluxes from the axial-direction and openings of thefirst and second magnetic shield side wall bodies into the cylindricalspace.

According to another embodiment, around the joint magnetic shield sidewall oppositely arranged of the first and second magnetic shield sidewall bodies, a coil is wound in the axial line direction to causecurrent to flow therethrough, thereby preventing magnetic fluxes fromflowing from the gap formed between the joint magnetic shield side wallsoppositely arranged of the first and second magnetic shield side wallbodies into the cylindrical space.

Functional Effects of the Invention

The separate type magnetic shield apparatus of the present invention hasa high access performance to a magnetic shield space and permits veryeffective achievement of magnetic shield.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is an overall configuration view of an embodiment of theseparate type magnetic shield apparatus of the present invention; andFIG. 1( b) is a schematic configuration view of the separate typemagnetic shield apparatus.

FIG. 2 illustrates a state of the separate type magnetic shieldapparatus shown in FIG. 1 in which one of the magnetic shield side wallbodies is removed.

FIG. 3 is an overall configuration view of another embodiment of theseparate type magnetic shield apparatus of the present invention.

FIG. 4 is a schematic configuration view for describing the concreteconfiguration of the separate type magnetic shield apparatus of thepresent invention.

FIG. 5( a) is a view for describing the configuration of the magneticshield side wall body; FIG. 5( b) is a view for describing theconfiguration of a bulkhead magnetic shield member; and FIG. 5( c) is aview for describing the configuration of a magnetic shield flangemember.

FIGS. 6( a) and (b) are views for describing the configurations of otherembodiments of a magnetic shield side wall body.

FIG. 7( a) is an overall configuration view of an embodiment fordescribing the configuration of a characteristic portion of the separatetype magnetic shield apparatus of the present invention; and FIG. 7( b)is a view for describing the method for determining current to besupplied to a conductor.

FIG. 8 is a magnetic flux line diagram in a case according to theconfiguration of the present invention.

FIG. 9 is a magnetic flux line diagram in a case where the configurationof the present invention is not adopted.

FIGS. 10( a), (b) and (c) are overall configuration views describingother embodiments of the separate type magnetic shield apparatus of thepresent invention.

FIGS. 11( a) to (c) are magnetic flux diagrams for describing theprinciple of the present invention.

FIG. 12 is an overall configuration view illustrating an example of theconventional separate type magnetic shield apparatus.

BEST MODE FOR CARRYING OUT THE INVENTION

The separate type magnetic shield apparatus of the present inventionwill now be described further in detail with reference to the drawings.

Embodiment 1 (Overall Configuration of the Separate Type Magnetic ShieldApparatus)

FIG. 1( a) is an overall configuration view illustrating an embodimentof the separate type magnetic shield apparatus 1 of the presentinvention. FIG. 1( b) is a schematic configuration view illustratingonly main parts for describing the overall configuration of the separatetype magnetic shield apparatus 1 shown in FIG. 1( a).

In the separate type magnetic shield apparatus 1 of the presentinvention, the layout is such that the longitudinal direction of theoverall structure is horizontal, and the apparatus has a plurality ofmagnetic shield side wall bodies 2 extending in the longitudinaldirection. According to the embodiment shown in FIGS. 1( a) and (b), themagnetic shield side wall body 2 has a first magnetic shield side wallbody 2A and a second magnetic shield side wall body 2B extending in thelongitudinal direction.

According to this embodiment, the first magnetic shield side wall body2A and the second magnetic shield side wall body 2B form, in a statearranged oppositely as shown in the drawing, a substantially cylindricalspace S around a longitudinal axial line Y-Y extending horizontally inthe interior.

Although the arrangement of the first magnetic shield side wall body 2Aand the second magnetic shield side wall body 2B is not limited to thefollowing one, these bodies 2A and 2B should preferably be arrangedright-left symmetrically relative to a vertical plane Vp passing throughthe longitudinal axial line Y-Y of the cylindrical space S. Alsopreferably, the first magnetic shield side wall body 2A and the secondmagnetic shield side wall body 2B are arranged up-down symmetricallyrelative to a horizontal plane Hp passing through the longitudinal axialline of the cylindrical space S.

When the first magnetic shield side wall body 2A and the second magneticshield side wall body 2B are arranged right-left and up-downsymmetrically as in this embodiment, a portion having the lowest densityof magnetic flux lines is formed substantially at the center of thecylindrical space S of the separate type magnetic shield apparatus 1 asdescribed later in more detail. In this case, it is possible to-providea space having a magnetic gradient of substantially null.

In this embodiment, for the separate type magnetic shield apparatus 1,as in the case of the separate type magnetic shield apparatus 100described with reference to FIG. 12, any of the first magnetic shieldside wall body 2A and the second magnetic shield side wall body 2B, orboth the magnetic shield side wall bodies 2A and 2B can be made movable.In this embodiment, the first magnetic shield side wall body 2A is mademovable, and the second magnetic shield side wall body 2B is fixed. Theconfiguration is not however limited to this, but the reverse isapplicable.

As to the manner of separation, for example, as shown by a one-pointchain line in FIG. 1( a), the movable magnetic shield side wall body 2Amay rotate around an end in the longitudinal direction, or as shown by aone-point chain line in FIG. 1( b), the configuration may be such thatthe movable body 2A moves in parallel to the horizontal directionrelative to the other magnetic shield side wall body 2 b.

FIG. 2 illustrates a state in which the first magnetic shield side wallbody 2A is removed, to show the interior of the separate type magneticshield apparatus 1.

In this embodiment, as shown in FIGS. 1 and 2, a MCG detector 200 havinga substantially cylindrical shape such as SQUID gradiometers isinstalled from above of the apparatus, at a position substantiallycentral in the longitudinal direction of the separate type magneticshield apparatus by inserting the MCG detector 200 into the internalspace S of the separate type magnetic shield apparatus 1. A bed 201 forplacing a subject patient is provided spaced apart from the lower end ofthe magnetocardiograph 200 by a prescribed distance. The bed 201 may befixed to the fixed second magnetic shield side wall body 2B. It ispossible to use a configuration, as the case may be, in which a fixedbed is not installed on the separate type magnetic shield apparatus 1itself, but a bed holding the subject patient on it is carried into theseparate type magnetic shield apparatus 1. According to the separatetype magnetic shield apparatus 1 of the present embodiment, the subjectpatient or the subject patient and the bed can be brought into theseparate type magnetic shield apparatus 1 in a state in which the firstmagnetic shield side wall body 2A and the second magnetic shield sidewall body 2B are separated, thus providing very convenient operation.

(Magnetic Shield Side Wall Body)

The magnetic shield side wall bodies 2 (2A and 2B) will now bedescribed.

As described above, the first magnetic shield side wall body 2A and thesecond magnetic shield side wall body 2B in this embodiment shouldpreferably have a right-left and up-down symmetrical shape. In thefollowing description, therefore, when it is not required to distinguishbetween the first and the second magnetic shield side wall bodies 2A and2B, the first and the second magnetic shield side wall bodies 2A and 2Bwill be described generally as “the magnetic shield side wall bodies 2”.

Referring to FIGS. 1 and 2, the magnetic shield side wall bodies 2 havea magnetic shield outer side wall 3, having a curved shape in thisembodiment, for forming a cylindrical space S of the separate typemagnetic shield apparatus 1, and flat joint magnetic shield side walls 4(4 a and 4 b) vertically projecting upwardly and downwardly from theupper and the lower edges of these curved magnetic shield outer sidewall 3. Since, as described above, the first and the second magneticshield side wall bodies 2A and 2B have a shape right-left and up-downsymmetrical, the joint magnetic shield side walls 4 a and 4 b have alsothe same shape and dimensions.

In this specification for convenience sake, the inner peripheral surfaceside forming a concave surface of the curved magnetic shield outer sidewall 3 is called the inner side, and the outer peripheral surface sideforming a convex surface is called the outer side.

When the first magnetic shield side wall body 2A and the second magneticshield side wall body 2B are arranged in an opposite shape in theaforementioned configuration, the both curved magnetic shield outer sidewalls 3 and 3 are oppositely arranged, and in the interior, form asubstantially cylindrical space S around the longitudinal axial linesY-Y extending horizontally. In this case, the both joint magnetic shieldside walls 4 (4 a and 4 a) provided above the curved magnetic shieldouter side wall are arranged apart from each other by a prescribeddistance (w) (see FIG. 4).

The MCG detector 200 is therefore installed by inserting it from the gapof the both joint magnetic shield side walls 4 a and 4 a formed at aboutthe center in the longitudinal direction of the separate type magneticshield apparatus 1 into the interior of the separate type magneticshield apparatus 1.

The gap between the both joint magnetic shield side walls 4 a and 4 apositioned above should preferably be the narrowest possible gap asdescribed later in detail. For this purpose, as is understood byreferring to FIGS. 1 and 4, a plurality of, or two in this embodiment,bulkhead magnetic shield members 5 are arranged at equal intervals (w1),extending in the longitudinal direction of the separate type magneticshield apparatus 1 and at substantially the same height position as thejoint magnetic shield side walls 4 a and 4 a in the gap between the bothjoint magnetic shield side walls 4 a and 4 a. By providing thesebulkhead magnetic shield members, there is available a function ofpreventing a disturbing magnetic field coming from the Y-Y axialdirection (see FIG. 1( b)) from flowing into the cylindrical space.

As is well understood by referring to FIGS. 1 and 4, for the purpose ofattaching the MCG detector 200 to the separate type magnetic shieldapparatus 1, at the position of installation of the MCG detector, thebulkhead magnetic shield member 5 is manufactured by curving it in thejoint magnetic shield side wall 4 a side into a

-shape, and forms an attaching opening 8 for the MCG detector 200.

In this embodiment also, as described above, a shape symmetrical in theright-left direction and the up-down direction is achieved so as to forma portion with the lowest density of magnetic flux lines at almost thecenter of the cylindrical space S of the separate type magnetic shieldapparatus 1 and so as to achieve a magnetic gradient of substantiallynull.

In this embodiment, therefore, as shown in FIGS. 1 and 2, a plurality of(two in this embodiment) bulkhead magnetic shield members 5 extending inthe longitudinal direction of the separate type magnetic shieldapparatus 1 are arranged at equal intervals (w1) even in the gap betweenthe both joint magnetic shield side walls 4 b and 4 b arranged belowwhere a MCG detector 200 is never installed. As in the structure of thegap between the two joint magnetic shield side walls 4 a and 4 a above,the bulkhead magnetic shield members 5 form a

-shaped curve to prepare an opening 8 a.

Varied Embodiment

As a varied one of this embodiment, as shown in FIG. 3, magnetic shieldflange members 6 may be provided at both end openings in the axial linedirection of the first and the second magnetic shield side wall bodies2. More specifically, flange members 6 having a prescribed width areprovided at both ends in the longitudinal direction of the curvedmagnetic shield outer side wall 3 in projection into the cylindricalspace S and in the radial direction.

This flange member 6 has a function of reinforcing the magnetic shieldside wall bodies 2. Particularly, installation of the flange member 6gives a function of preventing a disturbing magnetic field coming fromthe Y-Y axial direction (see FIG. 1( b)) from flowing into thecylindrical space S. As described later, it is now possible to supplycurrent by winding a coil 41 around this flange member 6, and further,to inhibit the disturbing magnetic field coming from the Y-Y axialdirection.

(Concrete Structure of Magnetic Shield Side Wall Body)

A concrete structure of the magnetic shield side wall body 2 will now bedescribed.

As shown in FIG. 5( a), the magnetic shield side wall bodies 2 (2A and2B) composed of the curved magnetic outer side wall 3 and the upper andthe lower joint magnetic shield side walls 4 a and 4 b can be composedof supports 21 having the same shape as the curved magnetic shield outerside walls 3 and the upper and the lower joint magnetic shield sidewalls 4 (4 a and 4 b), and magnetic bodies 22 arranged on these supports21 (outer surface and/or inner surface). In FIG. 5( a), layered magneticbodies 22 are arranged only on the outer surface, forming magnetic bodylayers. In other words, the supports 21 have a curved member 21 a andjoint members 21 b vertically projecting from the curved member 21 a upand down, and magnetic body layers 22 are arranged on the outerperipheral surface of the curved member 21 a and on the outer surface ofthe joint member 21 b.

The bulkhead magnetic shield member 5 is also formed, as shown in FIG.5( b), by arranging magnetic bodies 22 on the surface (inner surfaceand/or outer surface) of the support 24 having the same shape as themember 5. In this embodiment, the magnetic bodies 22 are provided on theboth surfaces.

The magnetic shield flange member 6 can also be composed of, as shown inFIG. 5( c), a support 21 c having the same shape as the member 6, andmagnetic bodies 22 arranged on the surface (outer surface and/or innersurface) of this support 21 c. According to FIG. 5( c), the magneticbodies 22 are arranged only on the outer surface, thus forming themagnetic body layer. The support 21 c is made integral with the curvedmember support 21 a of the aforementioned curved magnetic shield outerside wall 3.

As the supports 21 and 24, preferably, paper, resins, FRP, nonmagneticmetals, and various other materials are applicable. In this embodiment,the supports 21 and 24 are prepared from carbon fiber reinforcedplastics.

For the magnetic body 22, a magnetic material such as permalloy isapplicable. For weight reduction, however, a Co-based amorphous magneticthin strip such as Metglas 2705M (name of commercial product: Metglas,Inc.) is suitably applicable as the magnetic body 22.

The magnetic body layer composing the magnetic body 22 should preferablybe composed by laminating a magnetic thin strips as described above intolayers. As the magnetic body layer 22, as described later in detail, asin the configuration described later, a plurality of magnetic bodylayers which should preferably be thicker than 20 μm and thinner than500 μm are laminated into layers.

Varied Embodiment

By achieving a lamination structure as shown in FIG. 6( a), it ispossible to efficiently prevent a disturbing magnetic field coming fromabove from flowing into the cylindrical space S via the gap between theboth joint magnetic shield side walls 4 a and 4 a.

FIG. 6( a) illustrates only the upper portions of the first and thesecond magnetic shield side wall bodies 2A and 2B, omitting the lowerportions. However, a similar structure may be used for the lowerportions. In this case, disturbing magnetic fields coming from below canbe efficiently prevented from flowing into the cylindrical space S viathe gap between the both joint magnetic shield side walls 4 b and 4 b.

Only the lamination structure of the upper portions of the first and thesecond magnetic shield side wall bodies 2A and 2B will be described withreference to FIG. 6( a). According to this embodiment, magnetic bodies22 are arranged in layers on the surface of the supports 21 having thesame shape as the curved magnetic shield outer side layers 3 and theupper and the lower joint magnetic shield side walls 4 (4 a and 4 a), onthe outer surface of the supports 21 in this embodiment, thus formingmagnetic body layers.

According to this embodiment, the magnetic body 22 is composed of aninner magnetic body layer 22A and an outer magnetic body layer 22Bbonded with a bond such as epoxy resin adhesive 25 on the outside ofthis inner magnetic body layer 22A. The inner magnetic body layer 22Aand the outer magnetic body layer 22B themselves can be composed bypiling up 10 to 30 magnetic thin strips each having a thickness of 20μm, or depending upon the size of the prepared side wall body to beprepared, by laminating further more layers, or furthermore piling uptwo or more such laminations.

Description will be made further in detail. In this embodiment, theinner magnetic body layer 22A is formed of a magnetic body layer 22Aafixedly arranged on the curved member 21 a of the support 21, and amagnetic body layer 22Ab fixedly arranged on the joint member 21 b,while extending to halfway upward from the magnetic body layer 22Aa tothe joint member 21 b of the support.

The outer magnetic body layer 22B is formed, on the other hand, of amagnetic body layer 22Ba fixedly arranged on the magnetic body layer22Aa of the inner magnetic body layer 22A by an adhesive 25, a magneticbody layer 22Bb fixedly arranged on the magnetic body layer 22Ab of theinner magnetic body layer 22A by the adhesive 25 while extending upwardfrom the magnetic body layer 22Ba, and a magnetic body layer 22Bcfixedly arranged on a portion of the joint member 21 b further abovewhere the magnetic body layer 22Ab of the inner magnetic body layer 22Ais not fixedly arranged.

The disturbing magnetic fields flowing through the gap between the bothjoint magnetic shield side walls 4 a and 4 a into the cylindrical spaceS are therefore first attracted by the magnetic body layer 22Bc of theouter magnetic body layer 22B formed on the joint magnetic shield sidewall 4 a, and flow to the magnetic body layer Ba via the magnetic bodylayer 22Bb, i.e., through the outer magnetic body layer 22B, whereby theflow into the cylindrical space S is prevented. Furthermore, thedisturbing magnetic fields flowing into the cylindrical space S areattracted by the magnetic body layer 22Ab of the inner magnetic bodylayer 22A formed on the joint magnetic shield side wall 4 a, and theflow to the magnetic body layer 22Aa, i.e., to the inner magnetic bodylayer 22A, whereby the flow into the cylindrical space S is prevented.

As described above, the same structure may be used for the lowerportions of the first and the second magnetic shield side wall bodies 2Aand 2B. In this case, the disturbing magnetic fields coming from belowcan be efficiently prevented from flowing through the gap between theboth joint magnetic shield side walls 4 b and 4 b into the cylindricalspace S.

Varied Embodiment

According to further another embodiment, furthermore preferably asdescribed in Patent Document 1 described in this specification in thesection of conventional art, magnetic shaking current can be caused toflow at least through the curved magnetic shield outer side wall 3 ofthe magnetic shield side wall body 2.

In this case, a magnetic material having square magnetization propertyis applicable as a magnetic body 22. As such a magnetic body, theaforementioned Co-based amorphous magnetic thin strip such as Metglas2705M is suitably applicable.

In this embodiment, particularly as shown in FIG. 6( b), a magnetic thinstrip such as Metglas 2705M having a width of 50.8 mm and a thickness of0.02 mm is arranged by continuously winding, to cover the innerperipheral surface and the outer peripheral surface of the curved member21 a in the support 21, and further, to cover the entire inner and outersurfaces of the joint member 21 b. This forms a laminated magnetic body22, i.e., a magnetic body layers 22 a and 22 b surrounding the support21. The magnetic body layer 22 should have a thickness of at least 1 μm.Usually, however, it has a thickness smaller than 2 mm. The magneticbody layer 22 should preferably have a lamination structure prepared bylaminating a plurality of magnetic body layers each having a thicknessthicker than 20 μm and thinner than 500 μm.

Furthermore, as shown in FIG. 6( b), a coil 30 for magnetic shaking iswound. The coil 30 is wound around at least a part of the magnetic bodylayer 22 in a toroidal shape.

More specifically, it suffices to wind the coil so as to surround theouter magnetic body layer, i.e., to surround the outer layer of themagnetic body layers and the support 21 in the axial line direction. Themanner of winding the coil is not limited to the above, but the coilwire may be wound so as to surround the inner layer 22 b of the magneticbody layer 22 and the support 21 in the axial line direction.

A shaking current is supplied to the shaking magnetic field generatingcoil 30 of each magnetic shield side wall body 2 so as to give to themagnetic body layer 22 a shaking time of, for example, at least 50 Hz ofcommercial frequency and up to 10 kHz.

(Concrete Dimensions of Separate Type Magnetic Shield Apparatus)

The separate type magnetic shield apparatus prepared in this embodimenthad the following concrete dimensions.

The magnetic shield side wall body 2 used a carbon fiber reinforcedplastic composite material having a thickness of 5 mm as a support 21,and composed of a Metglas having a width of 50.8 mm and a thickness of0.02 mm wound on the inner and the outer peripheral surfaces of thecurved member 21 a of the support 21, and further on the inner and theouter surfaces of the joint member 21 b so as to cover the entiresurface of the support 21.

Concrete Example:

The prepared magnetic shield side wall body 2 had the following concretedimensions: While referring to FIG. 4:

Inside diameter (D) of the curved magnetic shield outer side 60 cm wall3: Axial length (L) of the curved magnetic shield outer side 180 cm wall 3: Width (H1) of the joint magnetic shield side wall 4: 20 cmInterval (W) between the joint magnetic shield side walls 4 30 cm and 4:Width (H2) of the bulkhead magnetic shield member 5: 20 cm Interval (w1)of installation between the bulkhead magnetic 10 cm shield members 5:Width (w2) of the opening 8 of the bulkhead magnetic shield 28 cm member5: Width (w3) of the opening 8 of the bulkhead magnetic shield 28 cmmember 5:

(Magnetic Shield)

The magnetic shield of the separate type magnetic shield apparatus 1forming a feature of the present invention will now be described. Thepresent invention is based on the-utilization of the principle ofshielding effect described above with reference to FIG. 11( c).

According to the present invention, as shown in FIG. 7( a), conductors10 (10 a, 10 b, 10 c and 10 d) are arranged on the outer peripheralsurfaces (or as required, inner peripheral surfaces) of the curvedmagnetic shield outer side walls 3 and 3 of the first and the secondmagnetic shield side wall bodies 2A and 2B in the separate type magneticshield apparatus 1 having the above-mentioned configuration. Alsoaccording to this embodiment, the conductors 10 a and 10 b and theconductors 10 c and 10 d are connected into coil shapes, and aprescribed current i is supplied thereto by power sources 50 (50A and50B).

In this embodiment, the current i of the same intensity is supplied bythe power sources 50 (50A and 50B) to the conductors 10 a and 10 b andthe conductors 10 c and 10 d, and this can be varied in response to thenecessity. In other words, the conductors 10 a, 10 b, 10 c and 10 d canbe connected to different power sources, respectively, and the resultantcurrent can be adjusted to an optimum value.

In this embodiment, the four conductors 10 a, 10 b, 10 c and 10 d arearranged at prescribed intervals up and down, and right and left. Acurrent is supplied to the conductors 10 a and 10 c from the near sideto the far side in the drawing, and to the conductors 10 b and 20 d fromthe far side to the near side.

Also in this embodiment, the conductors a and b, and the conductors cand d are respectively composed of 20-turn coils, and a current of 10 to20 A is supplied in total to each coil, giving a satisfactory result.

According to this embodiment, in other words, referring to FIG. 8, thefirst and the second conductors 10 a and 10 b extending in thelongitudinal axial line direction are provided at positions verticallysymmetrical relative to a horizontal plane Hp passing through alongitudinal axial line Y-Y of the cylindrical space S on the curvedmagnetic shield outer side wall 3 of the first magnetic shield side wallbody 2A. Similarly, the first and the second conductors 10 c and 10 dextending in the longitudinal axial line direction are provided atpositions vertically symmetrical relative to a horizontal plane Hppassing through the longitudinal axial line Y-Y of the cylindrical spaceS on the curved magnetic shield outer side wall 3 of the second magneticshield side wall body 2B.

A current is caused to flow to the conductors 10 a and 10 c in the samedirection, and to the conductors 10 b and 10 d in the same direction. Inthis case, the current flowing to the conductors 10 a and 10 c and thecurrent flowing to the conductors 10 b and 10 d are different indirection.

This causes vertical deflection of a magnetic flux (H) formedhorizontally from the first magnetic shield side wall body 2A to thesecond magnetic shield side wall body 2B to up and down directions bymeans of magnetic fields produced around the first and the secondconductors 10 a and 10 b, and the conductors 10 c and 10 d, therebypreventing the flow of the magnetic fluxes into the cylindrical space S.

(Determining Method of Current)

An example of the determining method of current will now be describedwith reference to FIG. 7( b).

In this embodiment, the X-axis is in a direction perpendicular to theshield side wall extending horizontally; the Y-axis is in thecylindrical axis direction (i.e., the longitudinal axes Y-Y direction ofthe cylindrical space S in FIG. 1( b)); and the Z-axis is in thevertical direction.

The magnetic sensor 300 may be flux gate magnetic field sensors or thelike. In this embodiment, a tri-axial magnetic field sensor which is amagnetic field sensor based on the combination of the perpendicular axesX, Y and Z is used.

In this embodiment, furthermore, four magnetic field sensors 300 (300A,300B, 300C and 300D) are installed in an upper gap formed by the jointmagnetic shield side walls 4 a and 4 a of the separate type magneticshield apparatus 1, or more specifically in this embodiment, at twopositions near the longitudinal both ends and at two positions similarlyin the lower gap formed by the joint magnetic shield side walls 4 b and4 b. The magnetic field sensors 300 may be installed at two positions inthe upper and lower portions as the case may be.

Sums of the individual components measured by the individual magneticfield sensors are calculated and averaged. For example, current for theside conductors (coils) 10 a, 10 b, 10 c and 10 d can be determined fromaverage values of X-axis-direction values x1, x2, x3 and x4 of theindividual magnetic field sensors 300. The technology of controlling thecurrent for each conductor by using, for example, a PID control systemis publicly known, and a further description is omitted here.

(Magnetic Shielding Effect)

FIG. 8 is a magnetic flux line diagram illustrating the magneticshielding effect based on the present invention when a current issupplied to the conductors 10 a, 10 b, 10 c and 10 d.

Optimum positions of the conductors 10 a, 10 b, 10 c and 10 d areappropriately determined through experiments or the like with due regardto the configuration of the separate type magnetic shield apparatus 1.Usually, as shown in FIG. 8, a position at 30° to 60°, ordinarily at 45°relative to the horizontal plane Hp is preferable. The position is nothowever limited to this range.

As understood from FIG. 8, adoption of the above-mentioned configurationcauses magnetic fluxes (H) entering from left to right in FIG. 8 to bedeflected vertically under the effect of the magnetic field produced bythe conductors 10 a, 10 b, 10 c and 10 d and the fluxes never passthrough the curved magnetic shield outer side wall 3. The configurationof the present invention permits achievement of the shielding effect.

As described above, on the other hand, in a configuration in whichconductors 10 a, 10 b, 10 c and 10 d are not installed, magnetic fluxespass from left to right as shown in FIG. 9, and a shield effect isunavailable.

According to the separate type magnetic shield apparatus 1 having theconfiguration of this embodiment, there could be achieved a specificmagnetic permeability of 10,000 (this is also the case with theconfiguration of FIG. 9), a thickness of the magnetic body 22 of 2 mm, acenter portion diameter (D) of 60 cm, a width (H1) of 20 cm of the upperand lower joint magnetic shield side walls 4 (4 a and 4 b) (in thisembodiment, a bulkhead magnetic shield member 5 is not provided), aninterval of 30 cm between joint magnetic shield side walls 4 (4 a and 4b), resulting in a shield ratio of over 1,000.

In addition, since the configuration for performing magnetic shakingpermits achievement of a specific magnetic permeability of 500,000,these values are very realistic.

In this embodiment shown in FIG. 8, the outer far magnetic field (H) was1 G (Gauss); the magnetic field in the gap G of the joint magneticshield side walls 4 (4 a and 4 b) was 0.1 G; and that in the cylindricalspace S was smaller than 1 mG.

In FIG. 8, magnetic fluxes in the axial line direction of thecylindrical space S (i.e., cylinder axis direction (perpendicular to thepaper)), and fluxes in the vertical direction can easily be activelycompensated by an opposite phase magnetic field by the application ofthe technology described in the aforementioned non-patent document 2,i.e., as shown in FIG. 3, by installing a coil 41 on the flange member6, and installing a coil 42 around the joint magnetic shield side walls4 and 4. For the purpose of making the first and the second magneticshield side wall bodies 2A and 2B separable, the coils 41 and 42 areindividually separably connected.

The present invention makes it possible to achieve high magnetic shieldperformance by effectively combining the action of attracting magneticfluxes of a ferromagnetic body and the action of rebounding magneticfluxes of current, thus forcedly causing bypassing of magnetic fluxes atdiscontinuous points even if not a continuous magnetic body.

Therefore, the high-performance separate type magnetic shield apparatusof the present invention can be expected to provide a high accessibilityto the shielded space and application in wide areas.

More specifically, the separate type magnetic shield apparatus of thepresent invention is applicable, for example, to an electron beamexposure device in the industry, for counter-measures for the electronmicroscope against environmental magnetic field among larger-scaledevices, for measurement of brain magnetic field and cardiomagneticfield in the area of measurement, and further, for biomagneticmeasurement of animals, and moreover, for measurement in nano-bio areausing magnetic beads as a label.

Other Embodiments

In the above-mentioned embodiment 1, the separate type magnetic shieldapparatus 1 has been described as having a configuration such that thelongitudinal direction of the overall structure becomes horizontal, andas having a magnetic shield side wall body 2 composed of a two-dividedbody comprising a first magnetic shield side wall body 2A and a secondmagnetic shield side wall body 2B.

However, the separate type magnetic shield apparatus 1 of the presentinvention can be composed of four, six or eight, or even more magneticshield side wall bodies 2, for example as shown in FIGS. 10( a), (b) and(c), when the apparatus becomes larger in size, or when forming anopening on the side is desired.

In other words, the separate type magnetic shield apparatus 1 of thepresent invention may have a plurality of magnetic shield side wallbodies extending in the longitudinal direction; the plurality ofmagnetic shield side wall bodies may form, combined with each other, asubstantially cylindrical space around the longitudinal axial lineextending horizontally in the interior; and at least any one of themagnetic shield side wall bodies may move relative to the remainingmagnetic shield side wall bodies, thereby forming a separableconfiguration.

The separate type magnetic shield apparatus 1 shown in FIG. 10( a) hasfour magnetic shield side wall bodies 2 (2A, 2B, 2C and 2D), and thefour magnetic shield side wall bodies 2 form a substantially cylindricalspace S around the longitudinal axial line extending horizontally in theinterior, combined with each other.

The separate type magnetic shield apparatus shown in FIG. 10( b) has sixmagnetic shield side wall bodies 2 (2A, 2B, 2C, 2D, 2E and 2F), and thesix magnetic shield side wall bodies 2, combined with each other, form asubstantially cylindrical space S around the longitudinal axial lineextending horizontally in the interior.

The separate type magnetic shield apparatus 1 shown in FIG. 10( c) haseight magnetic shield wall bodies 2 (2A, 2B, 2C, 2D, 2E, 2F, 2G and 2H),and the eight magnetic shield side wall bodies, combined with eachother, form a substantially cylindrical space S around the longitudinalaxial line extending horizontally in the interior.

Even in these embodiments, each magnetic shield side wall body 2 has aconfiguration similar to that of the magnetic shield side wall body 2described in embodiment 1, and each has a magnetic shield outer sidewall 3 having magnetic bodies combined with each other, forming acylindrical space S in the interior, and joint magnetic shield sidewalls 4 (4 a and 4 b) having magnetic bodies projecting outward in theradial direction from the both-end edges of the magnetic shield outerside wall 3.

Furthermore, in this embodiment as in embodiment 1, conductors 10 (10 ato 10 d) extending in the longitudinal axial line direction of thecylindrical space S are provided in the embodiment shown in FIG. 10( a)on the magnetic shield outer side wall 3 of the magnetic shield sidewall body 2; conductors 10 (10 a to 10 f) extending in the longitudinalaxial line direction of the cylindrical space S are provided in theembodiment shown in FIG. 10( b); and conductors 10 (10 a to 10 h)extending in the longitudinal axial line direction of the cylindricalspace S are provided in the embodiment shown in FIG. 10( c). Current iscaused to flow through these conductors in a prescribed direction, anddisturbing magnetic fluxes coming horizontally from the magnetic shieldside wall bodies on one side to the magnetic shield side wall bodies onthe other side are prevented from flowing into the cylindrical space Sby deflecting the fluxes up or down by means of magnetic field producedaround the conductors.

In an example, in the embodiment shown in FIG. 10( a), a current iscaused to flow through the conductors 10 a, 10 c from the near side inthe drawing to the far side, and through the conductors 10 b and 10 dfrom the far side to the near side. In the embodiment shown in FIG. 10(b), a current is caused to flow through the conductors 10 a and 10 dfrom the near side to the far side in the drawing, through theconductors 10 c and 10 f, from the far side to the near side, andthrough the conductors 10 b and 10 e, a direction of current flow can beappropriately determined, depending upon the direction of the disturbingmagnetic field. When the disturbing magnetic field is perfectlyhorizontal, it is possible even to stop the flow of the current.

In the embodiment shown in FIG. 10( c), current is caused to flowthrough the conductors 10 a, 10 b, 10 e and 10 f from the near side tothe far side in the drawing and through the conductors 10 c, 10 d, 10 gand 10 h, from the far side to the near side.

The above-mentioned direction of the current is only an example, and thedirection may be appropriately changed, depending upon the installationenvironment of the apparatus.

In the aforementioned embodiments, as in embodiment 1, a plurality ofbulkhead magnetic shield members 5 having magnetic bodies are arrangedbetween the opposing both joint shield side walls (4 a, 4 a; 4 b, 4 b)of the neighboring magnetic shield side wall bodies 2.

Magnetic shield outer side walls 3, joint magnetic shield side walls 4,and bulkhead magnetic shield members 5 are formed by providing magneticbodies on supports, as in embodiment 1.

In this embodiment also, as in embodiment 1, the structure of eachmagnetic shield side wall body 2 may have a structure shown in FIG. 6(a). A coil may be wound in the longitudinal direction in a toroidalshape on each magnetic shield side wall body 2 as shown in FIG. 6( b),and a magnetic shaking current may be caused to flow therethrough.

Although not shown, in this embodiment also, as in embodiment 1,magnetic shield flange members 6 shown in FIG. 5 may be provided atopenings in the longitudinal direction of the magnetic shield side wallbody 2, and further, current may be caused to flow through a coilinstalled on this flange member, thereby preventing magnetic fluxes fromflowing from the both-end openings in the longitudinal direction of themagnetic shield side wall body into the cylindrical space.

Furthermore, as in embodiment 1, as shown in FIG. 3, current may becaused to flow through a coil wound in the axial line direction aroundoppositely arranged joint magnetic shield side walls 4 of theneighboring magnetic shield side wall body 2, thereby preventingmagnetic fluxes from flowing from the gap formed between joint magneticshield side walls 4 (4 a, 4 a; 4 b, 4 b) of the neighboring magneticshield side wall body 2 into the cylindrical space S.

The magnetic shield side wall bodies 2 surrounding the cylindrical spaceS have the same dimensions and the same shape, and as described as toembodiment 1, it is possible to provide a space having the lowestdensity of magnetic flux substantially at the center portion of thecylindrical space S of the separate type magnetic shield apparatus 1,where the magnetic gradient is substantially null.

In the above-mentioned embodiment 1 and other embodiments, the magneticshield side wall bodies 2, i.e., the magnetic shield outer side walls 3have been described as having a curved shape. These components mayhowever be linear (i.e., flat-shaped) as the case may be.

1-21. (canceled)
 22. A separate-type magnetic shield apparatuscomprising a plurality of magnetic shield side wall bodies in thelongitudinal direction; wherein said plurality of magnetic shield sidewall bodies are combined mutually to form therein a substantiallycylindrical space around the longitudinal axial line extendinghorizontally, and at least one of said magnetic shield side wall bodiesmoves relative to the remaining magnetic shield side wall bodies and ismade separable therefrom; wherein each of said plurality of magneticshield side wall bodies has a magnetic shield outer side wall bodyhaving one of the magnetic bodies which are combined mutually to formtherein said cylindrical space, and joint magnetic shield side wallshaving magnetic bodies which project from the both longitudinal endedges of said magnetic shield outer wall outwardly in the radialdirection to said cylindrical space; and wherein conductors extending inthe longitudinal axial direction of said cylindrical space are providedon said magnetic shield outer wall of said magnetic shield side wallbody to supply current therethrough; and whereby disturbing magneticfluxes coming from said magnetic shield side wall body on one sidehorizontally to said magnetic shield side wall body on the other sideare deflected upwardly or downwardly by means of the magnetic fieldproduced around said conductors to thereby prevent the magnetic fluxesfrom flowing into said cylindrical space.
 23. The separate type magneticshield apparatus according to claim 22, wherein a plurality of bulkheadmagnetic shield members having magnetic bodies are arranged betweenfacing joint magnetic side walls of neighboring magnetic shield sidewall bodies.
 24. The separate type magnetic shield apparatus accordingto claim 22, wherein said magnetic shield outer side wall and said jointmagnetic shield side wall are formed by providing magnetic bodies on asupport.
 25. The separate type magnetic shield apparatus according toclaim 23, wherein said bulkhead magnetic shield members are formed byproviding magnetic bodies on a support.
 26. The separate type magneticshield apparatus according to claim 22, wherein a coil is wound in thelongitudinal direction thereof and in a toroidal shape around each ofsaid magnetic shield side wall bodies, and magnetic shaking current issupplied thereto.
 27. The separate type magnetic shield apparatusaccording to claim 22, wherein a magnetic shield flange is provided ateach of the both end openings in the longitudinal direction of eachmagnetic shield side wall body, thereby preventing magnetic fluxes fromflowing into said cylindrical space from the longitudinal end openingsof said magnetic shield side wall body.
 28. The separate type magneticshield apparatus according to claim 27, wherein said magnetic shieldflange member is formed by providing a magnetic body on a support. 29.The separate type magnetic shield apparatus according to claim 27,wherein a coil is installed on said magnetic shield flange member tocause a current to flow therethrough, thereby preventing magnetic fluxesfrom flowing into said cylindrical space from the longitudinal openingsof said magnetic shield side wall body.
 30. The separate type magneticshield apparatus according to claim 22, wherein a coil is wound aroundsaid joint magnetic shield side wall oppositely arranged of saidneighboring magnetic shield bodies in the axial direction, and a currentis supplied therethrough, thereby preventing magnetic fluxes fromflowing from the gap formed between said joint magnetic shield sidewalls arranged oppositely of the neighboring magnetic shield side wallbodies into said cylindrical space.
 31. The separate type magneticshield apparatus according to claim 22, wherein said cylindrical spaceis formed by being surrounded by two, four, six or eight said magneticshield wall bodies.
 32. The separate type magnetic shield apparatusaccording to claim 22, wherein said magnetic shield side wall bodiessurrounding said cylindrical space have an identical size and shape. 33.A separate type magnetic shield apparatus comprising a first magneticshield side wall body and a second magnetic shield side wall body;wherein said first magnetic shield side wall body and said secondmagnetic shield side wall body form a substantially cylindrical spacearound the longitudinal axial line extending horizontally in theinterior in an oppositely arranged state, and at least any of saidmagnetic shield side wall bodies moves and is separable from the othermagnetic shield side wall body; wherein said first and second magneticshield side wall bodies each has a curved magnetic shield outer sidewall which has a magnetic body forming said cylindrical space in theinterior in the oppositely arranged state, and joint magnetic shieldside walls having magnetic bodies which project vertically from theupper and lower end edges of said curved magnetic shield outer side walland are spaced apart from each other and facing each other in aoppositely arranged state; wherein first and second conductors extendingin said longitudinal axial line direction are provided on said curvedmagnetic shield outer side wall of said first magnetic shield side wallbody to cause current to flow; wherein first and second conductorsextending in said longitudinal axial line are provided on said curvedmagnetic shield outer side wall of said second magnetic shield side wallbody to cause current to flow; and whereby disturbing magnetic fluxescoming from said first magnetic shield side wall body horizontally tosaid second magnetic shield side wall body are deflected up and down bymeans of magnetic fluxes produced around said first and secondconductors, thereby preventing the magnetic fluxes from flowing intosaid cylindrical space.
 34. The separate type magnetic shield apparatusaccording to claim 33, wherein said first magnetic shield side wall bodyand the second magnetic shield side wall body have right-left symmetricshapes relative to a vertical plane passing through said longitudinalaxial line of said cylindrical space.
 35. The separate type magneticshield apparatus according to claim 33, wherein a plurality of bulkheadmagnetic shield members each having a magnetic body are arranged betweensaid joint magnetic shield side walls opposing to each other of saidfirst and second magnetic shield side wall bodies.
 36. The separate typemagnetic shield apparatus according to claim 33, wherein said curvedmagnetic shield outer side wall and said joint magnetic shield side wallare formed by providing a magnetic body in each of the supports.
 37. Theseparate type magnetic shield apparatus according to claim 35, whereinsaid bulkhead magnetic shield member is formed by providing a magneticbody in each support.
 38. The separate type magnetic shield apparatusaccording to claim 33, wherein a coil is wound in a toroidal shape insaid axial line direction around said first and second shield side wallbodies, and a magnetic shaking current is supplied thereto.
 39. Theseparate type magnetic shield apparatus according to claim 33, whereinmagnetic shield flange members are provided in the axial direction endopenings of said first and second shield side wall bodies, therebypreventing magnetic fluxes from flowing from the axial-direction endopenings of said first and second shield side wall bodies into saidcylindrical space.
 40. The separate type magnetic shield apparatusaccording to claim 39, wherein said magnetic shield flange member isformed by providing a magnetic body in each of the supports.
 41. Theseparate type magnetic shield apparatus according to claim 39, wherein acoil is installed on said magnetic shield flange member to cause currentto flow therethrough, thereby preventing magnetic fluxes from theaxial-direction end openings of said first and second magnetic shieldside wall bodies into said cylindrical space.
 42. The separate typemagnetic shield apparatus according to claim 33, wherein, around saidjoint magnetic shield side wall oppositely arranged of said first andsecond magnetic shield side wall bodies, a coil is wound in the axialline direction to cause current to flow therethrough, thereby preventingmagnetic fluxes from flowing from the gap formed between said jointmagnetic shield side walls oppositely arranged of said first and secondmagnetic shield side wall bodies into said cylindrical space.